If you are preparing for a holiday abroad you need to know a little more. One session under a sunbed is not enough, no matter how brown you appear to go. These 'UVA tans' can wear off after a day. To get a tan that stays, and protects better, you need more exposure to UVB. This will stimulate increased production of pale melanin in the skin. To get a long lasting tan, the trick is to get as much pale melanin produced as possible, so it can sit there in the skin waiting to be tanned by UVA. The more tanned melanin there is in the skin, the slower your tan will wear off. You replace all your skin cells every 28 days or so, so if it is not topped up in time, after about four to six weeks your tan will gradually fade away.
So, how do you get more melanin in the skin? Answer: Time. It takes time for the melanin cells to make more melanin - at least 2 to 3 days to even start the process. It probably takes 3 to 4 weeks to get up to full production and you cannot speed this process up. You cannot rush your cells! During this 'waiting period' you will need approximately 8 - 12 sunbed sessions. This is enough to stimulate the biology, tan the melanin that is produced, but not so much that you burn or waste time and money on overexposure and its attendant risks.
It is important that the first two sunbed sessions are gentle, if there has been a rest from tanning. The first session should be one half the normal time for their skin type and the second three-quarters. People with sensitive skins should start with a one quarter session and add a quarter each time they visit. With 8 - 12 sessions over 3 to 4 weeks, sessions should be spaced 2, 3 or 4 days apart for best results.
The adaptation to sunshine is virtually the same process as above, except that there is much more UVB in sunshine. This means that with a similar exposure pattern to the sunbed course described above, only under 'raw' sunshine, your 'sun tolerance' would increase from about ten minutes to over five hours without the risk of getting sunburnt. A tanning programme under 'raw' sunshine can thus increase UV protection by up to 20 to 40 times. An identical tanning programme under a sunbed does not give nearly so much protection, so you still need to wear sunscreens when you go into the sun. Using a sunbed with lamps that emit a higher proportion of UVB will give better sun protection than those with only low levels of UVB. But because you can't stay under them as long, some people may find they don't tan quite as darkly as under the high UVA machines.
The above information supplied by Tanning Business Magazine (tanningbusiness.com - 'How to tan')